In the design of a vehicle steering wheel, several important performance requirements must be satisfied. These performance requirements include the capability of the wheel to minimize or prevent vibration during operation of the vehicle and to absorb energy during a vehicle impact to provide for the safety of the vehicle operator. Generally, a steering wheel of low mass leads to a smaller inertia which decreases the effect of road vibration and offers less resistance to turning. From a safety point of view, it is desirable to have a steering wheel collapse (or deform) upon impact by the body of a vehicle operator during an accident in order to absorb the energy of the impact over a longer period of time. This important safety feature is not achievable when the steering wheel is rigid.
In a vehicle where an air bag is employed to further protect the vehicle operator, it is important to design a steering wheel which works cooperatively with the air bag in order to maximize the energy absorption capability of the air bag and the steering wheel. Ideally, the steering wheel should tilt with the lower portion moving back and the upper portion moving forward or staying at its position to offer a broader area for support of the vehicle operator's body such that it works in combination with the energy absorbing effect of the air bag. The desirability to design an energy absorbing steering wheel made of a lightweight material adds another performance requirement in that the lightweight steering wheel not only has to be energy absorbing, but also has to be strong enough to function properly in the normal operation of a vehicle.
Many designs and constructions for lightweight steering wheels have been proposed in the past. For instance, U.S. Pat. No. 3,714,844 to Tsuda discloses a steering wheel consisting of a light frame integrally molded from a flat plate. The steering wheel disclosed has a frame with ring, spoke and boss portions wherein the spoke portion has cuts to absorb mechanical shocks, the ring portion is non-circular and the spoke portion encloses an air bag. The ring portion has a required bent or curved cross-section, the spoke portion has a concave-convex, bent or curved cross-section, and the boss portion has an aperture for mounting to the boss. The steering wheel requires complicated manufacturing process since each portion of the wheel has a different cross-section, and furthermore each portion may be made of a different material. None of the previously designed wheels has taken into consideration the requirement of having all the components of a steering wheel to fail or to yield at the same load and at the same time.
It is therefore an object of the present invention to provide a vehicle steering wheel that does not have the drawbacks of prior art steering wheels.
It is another object of the present invention to provide a lightweight vehicle steering wheel that has components of the wheel designed in such a way that all the components fail or yield at the same load and at the same time.
It is a further object of the present invention to provide a vehicle steering wheel that has a rim portion, a spoke portion and a hub portion made of a lightweight aluminum alloy containing at least 95% aluminum.
It is another further object of the present invention to provide a lightweight vehicle steering wheel that has a rim portion, a spoke portion and a hub portion where all portions have continuous downwardly extending flanges designed in such a way that all portions fail and yield at the same load upon impact by the body of a vehicle operator.
It is still another further object of the present invention to provide a lightweight vehicle steering wheel that has a rim portion, a spoke portion and a hub portion equipped with continuous downwardly extending flanges and is made of an aluminum alloy consisting of at least 95% aluminum and at least 1% magnesium such that all portions fail and yield at the same load upon impact by the body of a vehicle operator.
It is yet another further object of the present invention to provide a lightweight vehicle steering wheel that has a rim portion, a spoke portion and a hub portion with continuous downwardly extending flanges and is made of an aluminum alloy such that all portions fail or yield at a minimum load of approximately 650 pounds and continuously yielding at such constant load so that the impact load exerted on the body of the vehicle operator is not increased during such impact.